China is the Crucial Player; a Coup, the Critical Piece
Regarding the problem of nuclear-armed North Korea, there is only one diplomatic solution--and it isn't entirely diplomatic.
Instead of trying to engage--collaborate with--North Korea, the United States should engage China, which supplies the North with most of its food, fuel and armaments. The U.S. should ask China to implement the Chinese solution--a PLA-orchestrated military coup that would replace the current North Korean regime with a pliable junta committed to smashing the Kimist system.
Here's the diplomatic part: in return for a U.S. agreement to withdraw its nearly 30,000 troops from South Korea, the North's new rulers would abandon their arsenals of nuclear, chemical and biological weapons, terminate their country's alliance with nuclear-arming, Islamist Iran--and peacefully reunite with the South.
Regime change in Pyongyang … reunification with Seoul … Washington's withdrawal ... a roadmap to peace that starts in Beijing.